The present disclosure relates generally to LED-based lighting devices and in particular to a compact emitter for a warm-dimming and color-tunable lamp.
An LED-based light source requires a number of components. At the core are one or more LEDs, where the term “LED” (or light-emitting diode) refers to a semiconductor die or chip that emits light (typically in a relatively narrow frequency band) in response to applied current, optionally including a coating of phosphor or other wavelength-shifting material applied to a surface of the die. In addition to the LEDs, the light source typically requires some sort of support structure to provide electrical connections to the LEDs as well as mechanical robustness. An encapsulating material is also used to provide protection from the elements while allowing light to escape. This encapsulating material typically incorporates a lens, diffuser, and/or other optical structures to shape the emitted light; it may also incorporate phosphors or other color-shifting material to modify the color of the emitted light. The term “emitter” is used herein to refer to the combination of the LED(s), support structures, and encapsulating materials that can function as a light source. One or more emitters can be incorporated into a lamp (e.g., a light bulb, light fixture, or the like).
For some applications, it is desirable to provide an LED-based light source that has controllably variable light output. For example, some LED light sources can incorporate LEDs that produce light with different wavelengths (e.g., warm white and cool white light, or light of different colors such as red, green, blue, amber, etc.), and it may be desirable to vary the color of light emitted from the light source by varying the relative current supplied to different LEDs and/or to vary the brightness by varying the total current. To support such operations, an LED-based light source can include additional components external to the emitter. For example, a controllable driver circuit can be used to supply the desired amount of current to different LEDs in order to provide a desired color, and to adjust the relative and/or total current to provide color tuning and dimming. Further, the LED-based light source may have characterization or calibration data (e.g., a mapping from a desired color to a distribution of source currents that produces the desired color) that needs to be stored in memory somewhere within the light source, e.g., in a PROM (programmable read-only memory) connected to the emitter.